Polylactide (or polylactic acid) is a kind of resin including the repeating unit represented by the following general formula. Such polylactide resin is a material having proper mechanical strength coming close to prior petroleum-based resins in company with eco-friendly characteristics such as recyclability as a reproductive resource, less CO2 (a greenhouse gas) generation during the production than prior resins, and biodegradability by moisture and microorganism in landfill, because it is based on a biomass unlike prior petroleum-based resins:

As the preparation method of the polylactide resin, the method of carrying out a direct polycondensation of lactic acid or a ring opening polymerization of lactide monomer in the presence of organic metal catalyst has been known. Among them, the direct polycondensation method is very difficult to eliminate moisture which is a by-product effectively because the viscosity increases rapidly in the process of the polycondensation. Hence, it is difficult to obtain the polymer having high weight average molecular weight of 100,000 or more, and thus it is difficult to secure sufficient physical and mechanical properties of the polylactide resin. Meanwhile, the ring opening polymerization method of lactide monomer is more complicated in the preparation process and requires higher cost than the polycondensation because the lactide monomer is prepared from a lactic acid in advance, but it has been commercially used because the resin having relatively high molecular weight can be relatively easily obtained through the lactide ring opening polymerization using an organic metal catalyst and the control of polymerization rate is favorable.
Such polylactide has been mainly used for disposable packaging/container, coating, forming, film/sheet, and fiber, and recently, it is actively being attempted to use the polylactide resin for semipermanent uses such as a mobile phone case or a vehicle interior, after mixing the same with prior resins such as acrylonitrile-butadiene-styrene (ABS), polycarbonate, polypropylene, and the like so as to reinforce the properties. However, the polylactide resin has a weakness in its own properties, being hydrolyzed by the catalyst used in the preparation or moisture in the air.
Particularly, when the polylactide resin or a copolymer including the same is processed into a film and used as a disposable packaging material, the weakness in the properties such as weak impact resistance and bad flexibility is a great setback for various market extensions.